System and method for channel interleaver and layer mapping in a communications system

#The present invention relates generally to wireless communications, and more particularly to a system and method for channel interleaver and layer mapping in a communications system with spatial multiplexing.

#The increasing demand of wireless high data service has motivated various standards bodies such as the Third Generation Partnership Project 2 (3GPP2), the Third Generation Partnership Project (3GPP) and IEEE-802.16 to develop various wireless systems supporting faster data rate, higher spectral efficiency and more reliable communication such as Ultra Mobile Broadband (UMB), Long Term Evolution (LTE), and wireless Metropolitan Area Networks (MAN), respectively. Additionally, since multiple input, multiple output (MIMO) operation offers significant increases in data throughput and higher spectral efficiency without additional bandwidth or transmit power, MIMO is considered as an essential technology in providing the high data rate and increased system throughput in the various standard bodies.

#Currently, LTE offers only MIMO in a downlink (DL) portion of a communications system, with support for up to two (2) codewords and four (4) transmit antennas, wherein DL refers to the transmission from the base station to a user equipment (UE). As used herein, a codeword refers to an encoded and modulated symbol sequence corresponding to an information block, such as the transport block defined in 3GPP specifications. No symbol-level channel interleaver was defined for LTE downlink because the time-frequency diversity due to the turbo internal interleaver and the rate matcher was found to be sufficient. Additionally, codeword to layer mapping was defined for LTE downlink without special consideration of successive interference cancellation (SIC) receiver.

#For a more complete understanding of the embodiments, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

#FIG. 1 is a flow diagram of LTE downlink physical layer processing;

#FIG. 2a is a diagram of codeword-to-layer mapping of one codeword to one layer;

#The making and using of the embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

#The embodiments will be described in a specific context, namely a communications systems adherent to 3GPP LTE and LTE-Advanced technical standards. However, the embodiments may be applicable to other wireless communications systems, such as those that conform to UMB, WiMAX, and so forth, technical standards. Therefore, the discussion of LTE and LTE-Advanced wireless communications systems should not be construed as being limiting to either the scope or the spirit of the embodiments.

#FIG. 1 illustrates a flowchart of DL physical layer processing. First, up to two transport blocks (TB) are input and for each TB, a cyclic redundancy check (CRC) is attached to the TB at Transport block CRC attachment unit 101. If the size of the TB is larger than a preset threshold, Code block segmentation and Code block CRC attachment unit 102 is used to split the TB into multiple code blocks (CB) and a CRC is attached to each CB. This may be performed to reduce the complexity of turbo encoder and decoder. If the TB is not larger than the preset threshold, then the TB may not be split into multiple CBs.